An automatic injector is a well known device for enabling an individual to self-administer a dosage of a liquid medicament subcutaneously or intramuscularly, usually in an emergency situation. Automatic injectors are used, for example, to treat anaphylactic (severe allergic) reactions and to administer antidotes for certain poisons, such as chemical nerve agents and various drug compositions such as diazepan. An advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile condition capable of storage in such condition for an extensive period of non-use, during which period immediate injection of the stored dosage may be accomplished at any time under the most severe emergency conditions. For example, automatic injectors have heretofore been manufactured and sold containing nerve gas antidotes for use under chemical warfare conditions. In addition, units of this type have been proposed for use in administering antiarrhythmic medicaments under emergency conditions relating to heart attack medical situations. As another example, injection devices of this type have been marketed containing a dosage of epinephrine as an antidote for counteracting severe allergic reactions, such as from bee stings and the like.
A typical auto-injector has a housing, inside of which is a cartridge. The cartridge has one or more chambers containing medicament compositions or components thereof and is adapted to be attached to a needle assembly. The cartridge can hold either a pre-mixed liquid medicament or a solid medicament and a liquid that are to be mixed prior to injection. The housing carries an actuation assembly with a stored energy source such as, for example, a compressed spring. Activation of the actuation assembly causes a sequence of movements, whereby the needle extends from the auto-injector into the user such that the medicament compound is subsequently forced through the needle and into the user. If the auto-injector is of the type designed to carry plural components of the medicament composition in separate, sealed compartments, structure may be included that forces the components to mix when the actuation assembly is activated. After delivery of the dose of medicament into the injection site, the needle remains in an extended position.
It is important that the user of an auto-injector learn its proper operation and become comfortable with its use. Users should not hesitate to inject themselves, either from fear of using the device or for lack of knowledge in the proper use of the device, at the critical moment when injection is required. However, it is impractical for individuals to train with automatic injectors by repeatedly injecting themselves with a hypodermic needle. Thus, there is a need for a device that simulates the operation of an auto-injector whereby the user can practice and become familiar with the auto-injector's operation prior to dispensing any medicament. Training with such a device should prevent improper administering of the medicament, improper orienting of the auto-injector, and premature removal of the auto-injector prior to the full dispensing of the medicament.
Various training devices have been developed that enable a potential automatic injector user to become acquainted with its use. Examples of known training devices are disclosed in U.S. Pat. Nos. 3,426,448; 3,795,061; 4,640,686; 5,037,306; and 5,071,353.
While the aforementioned U.S. patents relating to training devices have been effective in simulating the action of the automatic injector, they are not very user-friendly in that they each require some awkward procedure to recock the training device for reuse. For example, in the aforementioned U.S. Pat. Nos. 5,071,353, and 3,795,061, an auxiliary recocking tool must be used. In U.S. Pat. Nos. 3,426,448 and 5,037,306, a manual manipulation of the device is required before the prod member (which is a blunt elongate member that outwardly projects from the forward end of the training device housing to simulate the outwardly projecting hypodermic needle) should itself be physically forced back into the body of the training device, for example, by being thrust against a surface. In U.S. Pat. No. 4,640,686, no prod member is provided, and the training device must be reset or recocked by placing a safety pin element on a horizontal surface and then moving the training device downwardly onto the safety pin element until an opening in the training device fully receives the pin.
From a utility standpoint, a training device should be made to closely simulate the action of an automatic injector. The training device should also be capable of repeated use and of being made ready for reuse very easily. U.S. Pat. Nos. 4,640,686 and 5,567,160, both of which are assigned to the assignee of the invention, disclose training devices that can be easily reused. These training devices, however, do not simulate the operation of an auto-injector having sharps protection (i.e., an auto-injector whereby a cover member is provided such that the user is not exposed to the used needle of the auto-injector). From a commercial standpoint, training devices should be made as inexpensively as possible. It is an object of the invention to provide an injection training device that is relatively inexpensive to manufacture and simpler to use than those training devices known in the prior art.